Hi guys. I have been reading on this sight for a few years now. I have gotten a lot of good tips from you guys that have helped, so i'm enlisting your help on this project of mine. I bought a 91 z28 a year ago and since then it has been my baby. So far not much has been done other than the basics and a lot of research.

I have a 5.7 ltr tuned port with a 7oor4 and 3.23 gears. I have done a throttle body bypass, airfoil, k&n filters and than is about it. I recently purchased the superram base after much reading and thought it the best option. Next im going to buy either the accel runners so they will match up with the baseplate with no problem and as i understand it they leave a bit more room for porting. Or, my other option was the tpis/as&m runners, but i havent decided so any help there would be good aswell. When i get the two put together im going to port the plemum and get an adjustable fuel pressure regulator. I also need to know if this setup is going to need a prom change or not. I have speed density set up and its a little more sensative to intake changes as i hear it.
Next i am going to purchase hooker 2055s that are jet hot coated and a flowmaster exhaust with a low resistance cat. One dilema i have found so far is that fact that i have dual cats and hooker doesnt make 2055s with dual cat ypipe. Should i go with single cat setup and ditch the dual or customize a dual y?
That is about all the plans i have so far. I dont know what else to do to be the most effective. AS far as a cam goes, i would like somthing without a reall lopey idle. Any advice you have for me would be much appreciated.
So my goal is to break into the 12s and still have a daily driver for the least amount of money spent. Im asking a lot but let me know

 

I broke 12.99 and 12.95 with my full bolt on 89 L98 car. 3460 lb race weight in the cold winter air Runs 13.2-13.3's in average summer heat

So your just a mild cam swap away from being a solid 12 second car provided everything else is there

My car had a holley stealth ram but you can get away with TPI parts. Just port them abit if you can. Especially around the intake port running into the heads, thats the tight spot

Either runners will be fine, i like the TPIS big tubes or AS&M's if you can find them. Else a set of SLP runners that are siamesed are a great choice


It wont need a tune with those changes but realllly could benefit from one. thats gonna be the hardest thing. IF you cant do it yourself, i suggest you read up on how and learn how. Else you need to find someone that can do that for you.

Cam swap will definately need the tune. For a mild cam i like the 502 grind from comp. 218/224. Lingenfelter has two good grinds as well, the 211/219 and the 213/219 i think it is All these cams will require some work to the heads to handle the lift of the cam and get some screw in studs. About 200-300 bucks in machine work or so.

Run the hooker 2055's with single cat if you can, else install both cats on the hooker y-pipe or do a custom y pipe

ORRRR look into dyno don's headers and y pipe. His are the best stuff going for our cars that are smog legal. Similar price too. PM Dyno Don

next will be the most important for your timeslips. drag radials/drag DOT slicks and converter. Something with 2800 rpm stall speed atleast. That will get that car off the line. Some suspension bolt ons, you should cut 1.7x 60 foots easily with that car, and go mid high 12's depending on the cam. Full bolt ons should be pretty close to matching what my car has done. Low mid 13's in most weather days with 2800 stall/3.23 gear

 

Thanks a ton for the quick response. I also wanted to know if i should regear my rearend to 3.73. I know it might hurt my top speed but not as concerned with that as a good launch to make the car more fun. What about injectors. Will 19 lbph injectors after all is said and done be enough or should i swap them for bigger injectors and at what stage of the process should i do it. Also, if you could give me some good info on what and where i could get the stuff to program my own proms that would be awsome. I have been meening to do that for quite some time. Between my brothers and i we have four third gen camaros , and learning how to program proms would help us all out. I need to know where to get all the supplies and how much to expect to spend. As far as maching the heads, what all should i have done? Is it better to buy aftermarket or can i get into the twelves with well machined cast iron heads? thanks again

 

Well, depending on your final build plans 3.23 gears can be plenty to get into the 12's, especially with TPI. I prefer 3.42 gears tho. 3.73's wouldnt be too bad either for a bigger cammed setup, but 3.42's will match TPI much better.

Injectors? I'd say 19's wont quite cut it. stock L98's have 22's adn they can get by but its best to replace old injectors with good 24lb units. Depends on the cam you run or if you run a different set of heads and intake that may require more fuel. 24's should cover MOST of the needs up to 350whp. Thats plenty for 12's and may go 11's in some cars

Chip burning stuff, i use Craig Moates stuff from Moates.net. Burn1 programmer, ALDL scan cable, software, 2 chips, and chip adapter for stock ECM for about 250 bucks. Software is called Tunerpro RT

head work, i'd get screw in studs and then valve guides cut down abit and new valve stem seals so the heads will handle more than .500 lift. Have them set the heads up to handle .550 lift and run a cam with around .500 lift. IF you are willing to spend more money, you can have a shop port the heads alittle and do a valve job for more flow. Its not totally necessary for a 12 second slip, but very beneficial to gain more flow. AFtermarket heads are better and if you can afford it, then go with a good aftermarket set.

A mild port job, mainly port clean up and bowl work you can expect to pay 200-400 bucks and valve jobs are i believe somewhere around 100-200 bucks as well last time i checked.

I dont think you will need all that but every little bit helps

Another thing to look at is machining the spring pockets wider to so you can install wider springs which generally are stronger so you can run a bigger more aggressive cam. However there are great smaller diameter springs that will work just as good and that will fit into the stock pocket i believe. AFR has a 1.27" spring and so does Patriot. They got a 1.26" or similar size spring with titanium retainers/locks/etc all for 250 bucks or something like that. thats a SOLID lightweight valvetrain for a good price. But you'd only really need the springs if they sell them seperately

 

Great read guys, look forward to seeing you hit your budget 12-sec runs. Bumping up to the 24# injectors worked well for me, since they needed to be replaced anyways. Ran fine for quite awhile until I got a tune. Better response now, plus the larger injectors gave me adequate space to build on.

 

Thanks for you replies guys, I am going to get some 24# injectors and i was also about to buy the hooker 2055 header. The lowest price i have been able to find is jegs. Do you know if anyone else sells them for cheaper? I am planning to have them jet hot coated, do they possibly sell them themselves? Hopefully my car is going to be pretty quick when im all done. I just had i painted a few months ago covette red. I bought all new weather seals from the local dealer here in AZ (which cost me my first born) and the car is looking really good. I also just bought some new recaro seats, full power leather with red trim. They are the old school early 90's style and i love them. They look great but they also cost me a ton but im going to be happy with them when they i get them in. I wil try and post pics of some of the stuff i am doing as i go. I have a strut tower brace i just put in that made a huge difference in the conering ability and soon i am going to order the spohn sub-frame connectors too. Life is good Any more tips and suggestions on anything i have talked about would be great. Thanks again
B.t.w. Do you guys know what aftermarket cam has the highest horsepower/torque for our l98 cars? I want keep the good amount of torque i have if not increase it to make the car more fun? Are the TPIS cams any good? And also i was planning on uprgrading the ingnition system. Would an msd blaster coil do me good, Better plug wires how much is too much or not enough ?

 

Hi guys, i have another couple of questions for you. Right now i have on the way to my house a set of the corvette aluminum heads for my car. They are the heads with the casting number 113 or somthing close. I was wondering waht all this is going to do for me if anything. I do know that the combustion chambers are smaller on these heads than the cast iron L98 heads. What all is going be involved in swapping them, and by that i mean what do i need to change, egr,injectors,ect.. I dont know if it possble to take the prom chip out of a 91 corvette and swap it into my camaro is it? aslo, i just purchased a set of lingenfelter/accel runners to go with my accell base. they have been extruded and honed. The guy i baught them from said he paid after shipping a little over 730 for them and i got a deal. How good is extude and honing and shood i also have it done on the intake manifold? All your input is helpfull guys so thanks a alot.

 

113 heads over stock L98 iron heads should get you 10 hp or so. better chamber design i think as well as higher compression and abit better intake flow but much better exhaust flow. That should help

As far as swapping them make sure you have a proper gasket for them. steel shims for iron heads wont really work well with that aluminum. Felpro does make a rubber coated shim for both aluminum and iron that supposively works. I'd give it a try.

EGR wont work as it sits, you need to run the corvette style egr tube from the header to the back of the TPI manifold.

you dont need injectors unless you dont have 22's already or have a cam swapped in yet, then get 24's

extrude hone is good but pricey. may beable to achieve better results with hand porting and abit of siameseing but extrude hone does have some good gains on TPI stuff

Stock L98 bin will work fine for now, you dont need a 91 vette bin but it should work i guess if your speed density as well. May work better since you basically have a corvette L98 now. Tunning would be great to have tho either way. with higher compression, aluminum heads, and intake mods always can use a nice tune

 

So far I haven't seen a stall converter, tires, or suspension mentioned. Tires & some suspension mods dropped .5 off my ET in my 91'.

Also, 3.73's suck... I have them & I'm going back to 3.23's. These motors even modded peak around 4600-4800. You want to be around 4900-5200 in the lights best case scenario. 3.23's with a 106 - 109 MPH trap on a 26" tire will set you around 4700-5000 RPM in the lights.

Just my and past experiences.

 

Thanks for the feedback. I will follow the advice on the gaskets and see how it works. I am also planning on buying the hooker 2055 package and put everything at one time over a loooong weekend. The 2055s come with the smog leagel piping and i was wondering if that were the case could i just run a tube from those to my old egr, or do i have to plug that one and use the egr port at the rear of the intake(the accell intake has both)?
Aslo my Z has about 160k on it and i doubt the injectors have ever been changed. They are overdue for a replacement, and i was planning on swapping them out during this whole process. Would it be wise to go ahead and purchase 24lb injectors or but new 22s in light of the fact that my car may never get a cam change? I am going to get fpr also to help do a bit of tuning on my own. Any suggestions on the f.p.r. and injectors as far as companies go, or should i stick to oem.
Last q,sorry for all fifty questions but i figure i should collect all the pearls i can while im talking to you guys. You told me that i should definetly port the exhaust on the cast iron heads. Would the new vette heads i just received today also bennefit from a porting job on the exhaust side or should i leave them alone? Thanks again

 

Thanks for you inpout iroc. I am interested to know what kind of suspension mods helped you shave .5 of of you overall e.t.? i am planning on putting subfram connecters on my car and hadnt planned on swapping torque converters for a higher stall speed but if it helped you out all that much i may just try it.
Aslo, i have been converted and am no longer planning on 3.73 gears for my rearend, i have been told in this forum that 3.42s are the way to go for our cars. The tuned port setup already has a launch that can hold its own against much faster cars, but i wouldnt mind alittle more so that is why i would like 3.42 gears in the rearend. Would you suggest that i not? Thanks foryou help

 

3.42s increase wheelspin off the line but a set of drag radials would help that

freind of mine that had a 91 l98 z with out taking off the valve covers ran 13.3s pretty consistantly with over 230k on the car
he keep his 3.23s added a 2500 converter slp torque arm lakewood lcas ported stock plenum and stock runners skinnys on the front and drs on the rear slp dual cat headers and loudmouth exhaust
it really dosnt take much to put these cars into the 13s but 12s thats a bit harder

 

A converter is an awesome bang for the buck, .3 - .5 ET drop with traction. All I have done to my car since I bought it was remove the front sway bar, BMR chrome moly LCA's, relo brackets, and BFG Drags. I bought everything used for under $200 and did the install myself. My car has a muffler MSD 6A, K&N's, 3.73's, a 52mm TB, and free mods. The TB and ignition are worthless mods from the previous owner, as are the gears. If you have a quiet stock rear that doesn't need any work, I would leave it alone. Especially being a DD, leave the lesser gear and get a converter to do the work rather than gears.

As for headers, I'd spring for the Dyno Don headers. I had the 2055's on one of my old cars, I wasn't impressed at all for the money, but this is comming from a guy who has a $900+ set of Kooks on his 4th Gen. I picked up a used set ofr SLP tri-y's for my own personal car. They make awesome TQ, I shaved .3 off my ET's when sawpping from stock manifolds on my old 86'. It was definately a great mod. I expect similar gains on this 91'.

As for cylinder heads, from everything I've seen... the 113 castings really aren't much - if at all better than the cast heads that come stock on our cars. I would at least have them econo ported before installing them. Basically, mild bowl work, and open up the throat behind the valves. The mild weight savings is about the only benefit I can see over the heads that come on our cars stock.

Well... that's my $0.10 for tonight.

 

the tubes on the headers are for AIR not EGR. What you need to do keep your stock EGR valve where it is, and get a EGR kit from Scoggin dickey to hookup to the accell base thru the back port of the manifold. If you dont buy the kit, go make one. Basically a flange to mount to the back of the TPI base manifold and run a tube to the header tube. That makes EGR work.

i've run 2.77's to 3.27's to 3.42. The 3.42's i loved, and with TPI it works very well. Although 3.23's are a good choice, you cant go wrong especially with your goals.

For injectors i'd get 24's but thats because you need a cam change to hit consistant 12's. you can touch high 12's with bolt ons with drag tires/ higher stall converter and fairly light car in great weather. I've done that. But to get 12's consistantly you need slightly larger cam

 

I'm going to test that theory and push the envelope with my own personal car. I have a pile of mods on a shelf in my garage, the install-palooza starts in a few weeks. Hopefully BBK releases that intake they keep dangling in front of us. It is part of my plans with this car.

 

Thanks guys. Good knews! the heads and runners got here this week and the runners are like glass on the inside!! i am way stoked about that. The corvette heads look like the have some miles on them but otherwise in good condition. Should i change springs valves purshrods ect... before swapping or is it not worth the cost? Thank you for the info on the egr plumbing and i will get on that. Now before i put all this on my car in about one months time, i want to clean up the heads a bit. The question now is, should i grab a how to book on head porting and do it myself or is that too risky as i have never ported before? I dont want to ruin these heads, so your help is great. If it is a delicate job i will save the money up and pay to have it done for me the right way.
I dont recall if i metntioned yet that between my brothers and i we have four camaros right now, all between 91-92 .My older brother has a b4c that is cool and naturally, if these mods screw my performance im going to be a laughing stock of my family, lol so i appreciate you guys a ton. Let me know what all on the heads needs to be opened up as i already have to open the intake ports on the heads bc of the larger accel ports. You said that i should open the pockets behind the valves, should i leave the exhaust port alone or nay? Oh ya, and what is the easiest way to compare port sizes to match them? do i use gaskets to compare?

 

good luck! I know 12's is possible with bolt ons. i hit 12.95 and 12.99 with 3 other 13.01-13.02 runs that same day with my bolt on HSR L98. more was in it but not much more. I think 12.8's were as far as it would have gone. This was in 49 degree air at 1200 feet with a density altitude of 188 ft, or near sea level PERFECT conditions

good late fall conditions it goes 13.2's

bigger cam should be included to touch 12's more frequently just my experiences

 

I know your car well, and followed your progress. My old 86' was 350-400 lbs heavier than my 91', it ran consistent 13.00's cam only and bolt ons. It dipped into the high 12's in good weather. I didn't have a drag suspension or an efficient converter. So, the lighter car, better verter, better suspension - I'm hoping for similar ET's. But time will tell, right now the weather sucks for drag racing.

 

HI guys. Sorry it has been a while since i posted last, but i finally got the lingenfelter and accel intake and runners on my car. At the same time i ported the plenom to match and after many hours of labor and a lot of help from my brother it runs like a beauty! just a heads up, you dont need to change out proms for an intake swop of the same tpi set up/design. I had to plug a couple holes that were not used on the new intake but other than that, i was surprised how easily i went in. I had a lot of trouble getting the timing right but low and behold after much searching, my brother found out that the harmonic balencer had slipped and the timing line was off of were it should have been. Now the car runs stronger than ever. Let me know if anyone has any questions, headers are next and that should really bring the car to life. Oh ya, i dont know if i mentioned that i also had a cat-back flowmanster put on and limo tint and all i can say is dang my car looks nice! i also intalled recar leather heated and power seates in the driver and passenger. I should load pics soon. Thanks for you help everyone

 

Sounds good, any plans to go to the track soon? I'm waiting for at least a few months... the weather sucks here lately. 90+ degrees, and tropical storms flooding most of Central Florida.

 

I want to take it too the track soon. weather isnt so good right now were im from either . I live in phoenix az and its still sitting pretty @ 105 right now and not changing and day soon. I am getting closer to headers and am going to go with the hooker 2055s. my Z has dual cats and because hooker doesnt make a dual cat headers i am going to have to switch to a high flow cat . Does anybody have any good suggestions before i get started? Thanks for you help and i will let you know how the pocess goes.

 

I would pass on the hooker headers and get Dyno Don's instead. He is currently the only one I know of building dual cat headers for our cars. (Not to mention the fitment is great - do a search) Or, hunt up a used set of SLP's. I found a set of SLP Tri-Y's used here.

Why spend that kind of money and downgrade from a dual cat set up to a single? Just my $0.10

 

Does anyone know where a pic is of the stock dual cats and its routing? Or/and an aftermarket setup?

 

Magnaflow IIRC, makes a replacement Y with dual cats. I'm not 100% sure, but I believe Walker/Dynomax does as well.

 

I was wanting to look at one to see how its ran because I dont like how my custom y-pipe was made on my car. Its really no better then stock.

 

My car went 12.8 with the stuff in my sig. It's a bit different than you because it's a Corvette, but the premise should be the same.

The biggest thing I did was dyno tune my car. I was running 13.6's before the dyno tune. When we first strapped the car down it made 230 RWHP. When we were done (about 40 pulls later) the car made 261 RWHP. I picked up 31 RWHP and 50 RWTQ from just the dyno tune, on a basically stock car. After the tune I put on some 1.6 roller rockers and picked up another 6 RWHP across the board. Speed density really needs to be dialed in (even with mild mods like headers) at least that was my experience.

I probably would have gone faster without the 4.10 gears because I shift into 5th at about the 1000 foot mark and the car just falls over. However, the 4.10's make the car much easier to launch, so I am gaining ET from better 60 foot times. On street tires, with careful clutch management, the car usually goes 1.8XX. With street tires and the stock 3.45 gears the best I could do was a 1.95. With slicks and 3.45 gears, the best it ever did was a 1.80 - The same time I can now achieve with street tires and 4.10 gears. With the 4.10 gears and slicks it goes 1.75 pretty regular. Best ever is a 1.71.

Here's a dyno sheet before and after the tune:

 

Who did your tuning if you don't mind me asking?

 

I did it myself. I used to work for Staples Auto Engineering. www.staplesautoengineering.com

I brought my car down one Saturday and used the shop dyno to tune my car. I doubt most places would spend as much time as I did dinking with it, all in all I made 44 pulls on the dyno. I also did the rocker swap without unstrapping the car so I could see, definitively, how much RWHP I picked up from the rockers. I gained 6 RWHP pretty much across the board from the rocker swap. Unfortunately, it richened up the air/fuel ratio almost and entire point. I was too tired (I didn't finish the car until about 2 AM) to dink with the fuel curve anymore, and a 37 RWHP gain was enough to satisfy me, so I left it alone. I'm pretty sure I could eek another 8-10 out of it with another day of dyno time, but I don't work there anymore and $300+ for dyno time for what will be less than a 10 RWHP gain isn't worth it to me.

 

Gotcha... with the help of a few people I am going to try and "street tune" mine with a WB02. I'm pig rich at part throttle, and very lean @ WOT. I feel there's at least a tenth in my car as it sits.

 

I pulled a ton of fuel out of mine to make power, that's weird that you are lean at WOT.

If you want, I'll send you my .bin file. It's for a 91 Corvette, 6 speed, with long tube headers, no cats, and no emissions equipment. Everything on the car is pretty much stock, so if you are a lightly modded L98, it might be a good base line for you.

 

The pervious owner installed 24# LT1 injectors and DL'd a BIN file from this site. He said he changed the injector constant, but it seems like he didn't hit it dead on. Right now my car is stock other than a 52mm TB, UD crank pulley, !cats, magnaflow muffler. The TB is a waste, but it was on the car when I bought it. I'll be porting my plenum & base this weekend, and installing SLP Tri-Y's the following weekend. There's not much to do for bolt ons after that. I have some 1.6 rockers, but I have heard that the pushrod holes need to be enlarged. So I'm thinking I'll just save them for the new engine, and I doubt a set of runners would do much on a stock heads & cam car.

 

If you really want to do this here is what I have done and I ran 13.1. I have the B&M stage 2 Shift Kit. One step colder than stock spark plugs. 8.5 mm MSD Super conductor plug wires. 100 shot of Nx nitrous. SLP CAI Flowtec Headers (emissions legal) to a 3 inch high flow cat. 3 inch piping to the American Thunder Flowmaster Muffler with Dual outlets. That is all that constituted the 13.1/103 mph run.

1I have now a 10 bolt rear with 373's (had 323's) and a Detroit locker. Mickey Thompson M/T drag radials. Adj. Lower Control Arms from BMR fabrication (to eliminate wheel hop). Everything else is stock and this will be a 12.5 (educated guess) car. No crazy head work or anything.

Good luck With your Choice!!! I hope this helped!!!

~Chris

P.S. this set up cost about 5 grand max I paid about 3500-4000 because I did all the installs my self (I have access to a lift)

 

Sorry its been a while since i replied. Thanks again for all your input. So Let me list again averything i have done to my car to date and what my near future plans are.
k&n filter
msd coil
bmr strut tower brace(worth every penny)
ported plenum
Lingenfelter/accell extruded and honed runners
Lingenfelter/accell intake manifold
flowmaster 3" cat back
limo tint
leather recaro seats
in dash dvd

We arent done yet. I gave my brother who has a 92 b4c a chip tuner. So far he has burned a chip for his car and said that it made quite a bit of difference. Soon he is going help me with my car and we should be able to squeeze a few for horsies out of it. Next on my list is spohn sub-frame connectors and hooker 2055s. I have worked to eliminate the bottlenecks in my tuned port system and once i get my headers on i am hopeing that they will really wake up my motor.

On the Shelf
i have in my possesion 2:73 gm gears and l98 corvette alluminum heads. Im open for suggestions of all kinds. thanks

 

I agree with the person that said go with the converter instead of the gears.
A good quality 9" locking converter around 2800 - 3000 stall will make a huge difference.
Good ones aren't exactly considered "budget" but if you look hard enough you can find a used one. It is well worth the effort.

 

Thanks for the advice. I will definetly do some research on it. My next question would be what brand and what kind of a difference could i expect as far as a 0-60 time or quarter mile, i know they are not cheap so is it worth the investment per improvement?

 

FTI all the way. His basic LS1 converter knocks off .8 in the 1/4 on an average LS1 car. I would expect at least half that in an L98 car. I am about to swap from an ACT 10" lock up converter to an FTI 10" lock up. I will post my results ASAP. A good converter is about $500 - $700. Don't skimp out, a cheap *** converter can come apart and wipe out your transmission.

 

Ok, so i called the guy down at fti and he quoted me 695 for their sle series i believe it was. It sounds like he knew what he was talking about and the torque converter does come with a three year warranty. My question is, is there any other companies that work well for our our 700r4s or is fti the company definetly to go with? I have only heard one recommendation and i would like to get a second opinion before i blow 700 dollars. Thanks again

 

I like Vigilante (Precision) converters.
I'll recommend the 9.5" lock-up version and the one with multiple disks is better if you can find one for the right price. If you're not planning on going faster than 12.0 then the single disk should survive that with no problem.
Sometimes you can find them used for $300 - $400.
http://www.converter.com/vigilante.htm